Lametschwandtner A and Minnich B (2023), Ocular microvasculature in adult Xenopus laevis...

XB-ART-59622

J Morphol 2023 Mar 01;2843:e21561. doi: 10.1002/jmor.21561.

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Ocular microvasculature in adult Xenopus laevis: Scanning electron microscopy of vascular casts.

Lametschwandtner A , Minnich B .

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The microvascular anatomy of choriocapillaris, iris, ciliary body, and superficial vascular hyaloid system of eyes was studied in the permanent aquatic Xenopus laevis by scanning electron microscopy of vascular casts and was compared with that published in two semiaquatic ranid species (Rana esculenta and Rana temporaria), and the urodelian species Triturus criststus carnifex. Results showed that the choriocapillaris in Xenopus consisted of a dense meshwork of wide capillaries displaying polygonal arrays at the scleral side with venules leaving the centers and arterioles supplied from the periphery. The choriocapillaris lacked the multilayered capillary meshwork described in ranids. Iris and ciliary body were supplied by nasal and temporal branches of the iridial artery, which either originated with a common stem from the hyaloid artery or arose as individual vessels from the proximal portions of the semicircular nasal and temporal branches of the hyaloid artery. These branches ran in the pupillary margin and supplied the two-dimensional capillary network of the iris, as well as the three-dimensional network of the ciliary body. Iris and ciliary body drained via parallel running vasa recta into the choriocapillaris. The superficial vascular hyaloid bed (system) was supplied by the hyaloid artery. This artery coursed along the scleral surface of the ventrotemporal choriocapillaris toward the ora serrata, where it bifurcated into a temporal and a nasal semicircular branch. Seven to 10 arterial meridional twigs arose from these branches and supplied the superficial hyaloid capillary bed. Capillaries drained into branches of the hyaloid vein, which ascended toward the ora serrata, where the hyaloid vein joined the temporal branch of the ciliary vein.

???displayArticle.pubmedLink??? 36719276
???displayArticle.link??? J Morphol

Species referenced: Xenopus laevis
Genes referenced: ddx4
GO keywords: eye development

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	Figure 1 Xenopus laevis, eye of an adult individual. Histomorphology. Parasagittal section at the level of the margin of the lens. Goldner staining. Shown are lower eye lid (lel), cornea (co), anterior eye chamber (aec), iris (ir), vitreous body (vb), lens (le) retina (re), choriocapillaris (chc) of choroid, sclera (sc), and eye muscles (eym). ld, lacrimal duct; sk skin.
	Figure 2 Xenopus laevis, eye of an adult individual. Histomorphology of the retina. Goldner staining. Shown are the retinal layers consisting (from the vitreous side to the scleral side) of ganglion cell layer (1), inner plexiform layer (2), inner nuclear layer (3), outer plexiform layer (4), outer nuclear layer (5), photoreceptor layer (6), retinal pigment epithelium (7), choriocapillaris (8), and the choroid (9). Seen are further blood vessels of the superficial hyaloid vascular system, which locate between vb and retina (arrows). Vessels of the choriocapillaris (asterisks) closely attach to the retinal pigmented epithelium. aa, arteriole; vb, vitreous body; vv, venule.
	Figure 3 Xenopus laevis, microvascular anatomy of the left eye of an adult individual. Vascular corrosion cast. Scanning electron micrograph. Scleral surface of choriocapillaris (chc). Proximal portion of the nasal branch of the ciliary vein (nbciv) is removed. Note undulating courses of temporal (tb) and nasal (nb) branches of the ciliary artery (cia). Asterisk marks the entrance site of the optic nerve. Inset: Adult female Xenopus laevis. Dorsal view. Note dorsally located small eyes (arrows). Arrowheads point at nostrils. civ, ciliary vein; fl, foreleg; hya, hyaloid artery; tbciv temporal branch of ciliary vein; vv, venule.
	Figure 4 Entrance site of the optic nerve (asterisk). Detail from Figure 3. Specimen slightly clockwise rotated. Scleral aspect. chc, choriocapillaris; hya, hyaloid artery; nbciv, nasal branch of ciliary vein; tbcia, temporal branch of ciliary artery; tbciv, temporal branch of ciliary vein.
	Figure 5 Xenopus laevis, vascular corrosion cast; scanning electron micrograph. Vascular pattern of the choriocapillaries (chc). Retinal surface. Detail. Note a small capillary glomus (arrow). Asterisk marks the entrance site of the optic nerve.
	Figure 6 Xenopus laevis, vascular corrosion cast; scanning electron micrograph. Arterial supply and venous drainage of the choriocapillaris. Detail. Scleral view. Note thin terminal ciliary arterioles supplying a polygonal array (outlined by dashed lines) from the periphery (arrowheads) and venules draining from centers (arrows). bcia, branch of ciliary artery; bciv branch of ciliary vein; civ, ciliary vein.
	Figure 7 Xenopus laevis, vascular corrosion cast; scanning electron micrograph. Origin of the iridial artery from the hyaloid artery and its bifurcation into a temporal branch and a nasal branch. Inset: Bifurcation of the hyaloid artery (hya) into nasal (nbhya) and temporal branch (tbhya) and site of origin of the stem of the iridial artery (ia) as seen after removal of overlying ciliary venules (civv). chc, choriocapillaris; civ, ciliary vein; hyv, hyaloid vein; ia, iridial artery; iv, iridial vein; nbhya, nasal branch of hyaloid artery; nbia, nasal branch of iridial artery; tbhya, temporal branch of hyaloid artery; tbia, temporal branch of iridial artery; vr, vasa recta.
	Figure 8 Xenopus laevis, vascular corrosion cast; scanning electron micrograph. Origin of nasal (nbia) and temporal branches (tbia) of the iridial artery from the corresponding branches (nbhya, tbhya) of the hyaloid artery (hya). chc choriocapillaris, civ ciliary vein. Inset: Bifurcation of the hyaloid artery (hya) into nasal (nbhya) and temporal branch (tbhya) and sites of origin of nasal (nbia) and temporal (tbia) branch of iridial artery from the former.
	Figure 9 Xenopus laevis, vascular corrosion cast; scanning electron micrograph. Microvascular anatomy of the ciliary body (cib). Corneal surface. Note the terminal ciliary arterioles (ciaa), which feed ciliary body vessels. chc, choriocapillaris; civv, ciliary venule; nbhya, nasal branch of hyaloid artery; nbia, nasal branch of iridial artery; pu, pupilla; vr, vasa recta.
	Figure 10 Xenopus laevis, vascular corrosion cast; scanning electron micrograph. Microvascular anatomy of iris (ir) and ciliary body (cib). Detail. Frontal view. Note an ascending terminal ciliary arteriole (ciaa). nbia, nasal branch of iridial artery.
	Figure 11 Xenopus laevis, vascular corrosion cast; scanning electron micrograph. Microvascular anatomy of the superficial hyaloid vascular bed (shvb) of the left eye of an adult individual. Frontal view. Spatially distorted vascular corrosion cast. Choriocapillaris, iris, and ciliary body are removed. civ, ciliary vein; hyv, hyaloid vein; mt, meridional twig; nbhya, nasal branch of hyaloid artery (hya); tbhya, temporal branch of hyaloid artery; tmt, terminal meridional twig.
	Figure 12 Xenopus laevis, vascular corrosion cast; scanning electron micrograph. Terminal portions of temporal (tbhya) and nasal branch (nbhya) of the hyaloid artery forming the terminal arterial meridional twigs (tmt). Note the lack of an anastomosis leaving the arterial ring open (encircled area). bhyv, branch of hyaloid vein; mt, meridional twig; rhyv, root of hyaloid vein; shvb, superficial hyaloid vascular bed.
	Figure 13 Xenopus laevis, vascular corrosion cast; scanning electron micrograph. Vitreal surface of the superficial hyaloid vascular bed (shvb). Detail. Note the short transition distances from an arterial meridional twig (mt) to hyaloid venule (hyvv). c, capillary; ia, iridial artery.
	Figure 14 Schematic representation of main ocular vessels of adult Xenopus laevis. 1, ophthalmic artery; 2, ciliary artery; 3, nasal branch of ciliary artery; 4, temporal branch of ciliary artery; 5, hyaloid artery; 6, nasal branch of hyaloid artery; 7, temporal branch of hyaloid artery; 8, nasal branch of iridial artery; 9, temporal branch of iridial artery; 10, meridional twig of nasal and temporal branch of hyaloid artery; 11, hyaloid vein; 12, iridial vein; 13, temporal branch of ciliary vein; 14, nasal branch of ciliary vein; 15, ciliary vein.